1. Field of the Invention
The present invention relates to a system for checking a program memory of a processing unit having a check module, the processing unit being made up of an instruction counter connected to the program memory, which has a register and the register is connected to a first changeover switch that sets the register content.
2. Description of Related Art
In the area of motor vehicle technology, the number of applications that are critical with respect to safety is growing constantly. At the same time, the complexity and the safety requirements of the circuits used in the motor vehicle technology are rising as well. This applies especially also to the hardware-specific circuits (ASIC). Meanwhile, the demands for checking the safety-related components are increasing. Thus it is also necessary to check the program codes that are integrated in a circuit or stored in an external memory and are used to execute safety-related applications.
Because conditionally executable jump instructions are able to influence the program run in a processing unit, preferably a processor core, the instruction flow at the output of the program memory is not always deterministic. This means that there exists no definite relation between input data and output data. Thus certain instruction addresses of the program memory are always addressed, while others are addressed only in a certain mode. For this reason, the program code cannot be verified by an efficient data block-based or data flow-based check mechanism.